How to explain and measure gender discrimination in labour markets are perennial questions. A large literature uses observational data and Blinder–Oaxaca decomposition methods, where the “unexplained” component is interpreted as discrimination. A weakness of this approach is that the magnitude of discrimination is sensitive to the number of observable factors included in the analyses. More recent analyses point to the importance of social norms and gender differences in economic and social preferences. The study of the motherhood penalty has a long tradition and the penalty seems to remain an important factor. More studies have been concerned with the efficacy of policies to the reduce gender gaps, such as paternal child-care leaves and female board quotas.